This invention relates to rotating union type coupling devices, and more particularly to sealing assemblies for rotating unions.
Rotating unions are used in applications to couple the outlet of fluid sources to rotating devices. For example, rotating unions are used extensively in the printing industry, the paper processing industry, in high speed drilling and boring transfer operations, high speed machine tool spindles, clutch and brake operations etc.
The rotating unions are used to conduct fluids such as water, air, hydraulic fluid, coolant, steam, hot oil, depending upon application, from a source to a rotating device. A sealing assembly within the rotating union provides the interface between the fixed outlet of the fluid source and the rotating device. The rotor shaft mounts a first sealing member for rotation therewith. A second sealing member is non-rotatably mounted within the housing of the union. The non-rotating member is urged into fluid-tight engagement with the rotating seal face under the force of a bias means, typically a spring arrangement. Eventually, leakage may occur around the seal because of scoring of the face of at least the rotating seal member. Because the rotating seal member is either permanently attached to the rotor, or is integrally formed with the rotor, replacement of a damaged or scored rotating seal member requires replacement of the entire rotor assembly. This is a difficult and expensive operation and requires considerable amount of down time for the apparatus on which the rotating union is used. Thus, it would be desirable to have a rotating union which includes a seal assembly which is readily replaceable.
Another factor is the material from which the seal members are formed. At the present time, it is common practice to use carbon graphite to ceramic seal combination in rotating unions. Although such materials provide a good seal, the seal faces have a relatively short useable lifetime. It would be desirable to have a seal assembly formed of a material which exhibits increased wear resistance.